基于三维有限元铸轧工艺模拟及工艺参数优化的Mg-Al合金晶粒细化(英文)

为了获得质量优异的镁合金薄板材并研究铸轧工艺参数对AZ31镁合金薄板材的温度场和热应力场的影响,基于铸轧的对称性采用ANSYS软件建立了三维几何和有限元模型。在ANSYS软件中采用smart-sizing算法进行网格划分。进行了一系列不同工艺参数下的三维温度场和热应力数值模拟。结果表明,随着浇注温度的升高,液相区和液固两相区的长度都增加;随着辊/薄板间接触的对流换热系数的增大,液固两相区的长度减小;随着浇注温度和铸轧速度的提高,两相区的长度增大。将优化的工艺参数(铸造速度2m/min、浇注温度640℃、换热系数15kW/(m2·℃)及水淬)用于镁合金铸轧试验,得到平均晶粒尺寸为50μm的镁合金板坯。三维仿真结果能更好地理解相变区的温度变化和铸轧过程中热裂纹的形成机理,为设计和优化镁合金铸轧的工艺参数提供帮助。

Grain refinement of Mg-Al alloys by optimization of process parameters based on three-dimensional finite element modeling of roll casting

To study the influence of roll casting process parameters on temperature and thermal-stress fields for the AZ31 magnesium alloy sheets, three-dimensional geometric and 3D finite element models for roll casting were established based on the symmetry of roll casting by ANSYS software. Meshing method and smart-sizing algorithm were used to divide finite element mesh in ANSYS software. A series of researches on the temperature and stress distributions during solidification process with different process parameters were done by 3D finite element method. The temperatures of both the liquid–solid two-phase zone and liquid phase zone were elevated with increasing pouring temperature. With the heat transfer coefficient increasing, the two-phase region for liquid–solid becomes smaller. With the pouring temperature increasing and the increase of casting speed, the length of two-phase zone rises. The optimized of process parameters (casting speed 2 m/min, pouring temperature 640 °C and heat transfer coefficient 15 kW/(m2·°C) with the water pouring at roller exit was used to produce magnesium alloy AZ31 sheet, and equiaxed grains with the average grain size of 50 μm were achieved after roll casting. The simulation results give better understanding of the temperature variation in phase transformation zone and the formation mechanism of hot cracks in plates during roll casting and help to design the optimized process parameters of roll casting for Mg alloy.